Do we have perfectionists here?
Been having a doubt: are we recommended to master every single lesson? I see a lot of people skip bonus rounds and translations and leave many skills (simply) "learned." I wouldn't have accepted that anyway...
Also, Duo should be able to recognize that when i click on a previous lesson that has an ugly zero/one heart on it, i'm simply trying to re-master this lesson. Ideally IMO the lesson should then turn into a brief exercise in which, errors made before are presented, knowledge re-tested, and the original, for-newbies content NOT repeated.
I would recommend you progress and learn more, without mastering, initially. Then come back, from time to time, and revisit things you haven't mastered. This will make you see the words again after a time, enhancing transfer to long term memory.
For example, today in German I worked on negatives, and finally mastered the food section. There are something like 13 non-golden boxes between those. I'll probably come back in a few weeks and pick up the few remaining lessons without 3 hearts.
If you work really hard on one section, but only over a short period of time, you won't learn it as deeply as you would by seeing it repeatedly over a longer time period.
Definitely a perfectionist here. I don't leave a lesson until I've completed it with three hearts remaining. A bonus round isn't "complete" until I've finished in under 2 minutes and, separately if necessary, finished with three hearts remaining.
This approach means that it takes me longer to progress onto new subjects, but it means that I get more practice on each lesson. Silly mistakes and typos can mean that I have to redo a single lesson over and over again - but that's a positive as I gives me more practice on that lesson.
I tend to leave at least a night's sleep before finishing with mastering. That way more will get committed to my longterm memory or force me to train until it does. Doing a whole unit in one day is not as good. Can't wait to become part of the new system where the system will account for memory degradation.
Learning new units first makes things harder, since you get sentences mixed with all the known words and forms, not just what you knew when first encountering the unit. So it's a good way to lessen the repetitiveness of the first lessons.